does it help? which way is best to do it? I have a B16A with DC 1 piece headers.

 

I've read about this for motorcycles, but never cars... a lot of people say that the wrap prevents the metal from dissipating heat and makes the metal brittle and more likely to break. I don't know how that will compare on a car, but I would think the effect would be even worse than on a motorcycle, where the pipes are exposed to the air.